CDproject always played with the lore a bit loose, so I'm sure the explanation will not be in line with book canon, but hopefuly it will be a good one.

My guess is some modified version of the Trials, less powerful but also less risky - maybe made possible due to her "herbal treatment" at Kaer Morhen. Or she just resumed the herbal treatment long term and these are the results.

Ciri has Elder Blood, so maybe that's why?

I could clearly see Ciri's green eyes at the beginning and at the very end.

She is a Witcher, i believe Triss and Gerald were able to find the mutigen needed in order to do the trial of grasses. In the show it came from Ciri's elder blood

Im interested to know the timeline too, and if Geralt really did retire with Yen.

I had always assumed Ciri would eventually become a Witcher, given her elder blood and fate tied to Geralt.

I'm not really feeling the new Ciri either, but CDPR didn't follow the book lore all that well. They confirmed in a tweet that indeed she went through the trial, and speculation tells that she may gave done so with the help of a witcher from another school, broken off from the school of the cat ( see the new medalion ). From the agresiveness she shows in the trailer I'm guessing they're going for a more Falka-like Ciri, which is intriguing.

But I admit I'm a bit disappointed with their decision to insist on the well established characters for the "new trilogy" as they call it. It feels very boring and safe, and frankly I though that their arcs were complete and it was time for something new. We'll see I suppose

Yeah I'm curious if the firey binding chain will be a mechanic. I figured the actual beheading part was just normal Witcher trophy collecting tho.

Has nothing to do with the Netflix series.

The monster in the trailer is assumably a Kikimora, which are relatively common, but hard to kill and therefore feared. They have a very hard chitinous shell and are agile, but if you manage to slice up the legs, you can get closer to its' weakpoints and therefore kill it.